A jackknife truck accident occurs when a tractor-trailer brakes too hard on a slippery road. This can happen in one of two ways. When the trailer wheels lock up, the trailer wants to continue sliding down the road past the tractor. This causes the back of the trailer to fishtail about the trailer hitch. Meanwhile, the tractor is braking without skidding. If the truck driver fails to recover from this, the back of the trailer will continue to fishtail forward while pivoting on the hitch until it forms the classic V with the tractor. Note that slippery conditions can mean snowy, icy, and even wet roads.

The second way that jackknifing occurs is when the tractor’s wheels lock up, which causes the tractor to pivot about the hitch while the trailer continues moving forward without skidding. This time, the tractor’s front end whips backward about the hitch and again forms the classic V with the trailer. Recovery from this type of jackknifing is impossible once the jackknife angle exceeds fifteen degrees.

To avoid jackknifing on a slippery road, the driver must apply brakes lightly while keeping the trailer perfectly lined up with the tractor. Applying brakes lightly is only possible when the truck has plenty of distance for slowing down. This means the driver must allow plenty of following distance, and remain focused on the traffic situation ahead so that he can start braking early when he spots trouble or a stop sign ahead.

Keeping the trailer in-line with the tractor means that the driver cannot brake while turning or while on a curve. This means that the driver must do all of his braking before entering a sharp curve on the road, let up on the brakes, and then turn his steering wheel. Avoiding a stopped vehicle ahead of the truck will require the truck to brake first and then turn, or to turn first and then brake.

Common Situations That Cause Jackknifing

A car cuts off a truck in slippery conditions, which leaves insufficient braking distance for the truck.

A car brakes hard in front of a truck that is following too closely on slippery pavement.

A truck driver fails to notice a problem ahead quickly enough to start braking in time.

A truck driver allows insufficient following distance for the road conditions.

A truck driver mistakenly attempts to brake while turning on slippery pavement.